Interest in fortification of foods with nutritionally beneficial lipids is growing. Unfortunately, these applications are limited by the fact that lipids are prone to oxidative deterioration. Indeed, the susceptibility of lipids to oxidation is a major cause of quality deterioration in food emulsions. Such food quality deterioration includes undesirable changes of flavor, texture, shelf-life, appearance and nutritional profile.
Current technologies utilize lipids in bulk form with the lipids being stabilized by exogenous food antioxidants. Nevertheless, these bulk lipids only show moderate oxidative stability. Further, drying and encapsulating lipids has also been used. However, this technology is limited by the high degree of non-lipid materials required and the loss of antioxidant protection once the materials are placed in a water-based food.
Recently, a great deal of research has been focused on oxidation of lipids in oil-in-water emulsions rather than bulk lipids due to the former being more commonly encountered in actual food products. In many studies of oxidation in oil-in-water emulsions, model emulsions have been prepared with synthetic surfactants [e.g. sodium dodecyl sulfate (SDS), dodecyltrimethylaminmonium bromide (DTAB), Brij and Tween] even though not all of these surfactants (e.g. SDS, DTAB, Brij) are approved for food use.
Unlike these synthetic surfactants, proteins represent GRAS food additives that can form physically stable emulsions. For example, the emulsifying properties of whey proteins have been studied for years. The polymerizations of whey proteins in whey protein-stabilized emulsions, the interactions between whey proteins and commonly used surfactants at the emulsion droplet surface, and influence of pH, CaCl2, sucrose, heat treatment and protein concentration on the stability of whey protein stabilized emulsions have been reported.
A better understanding of how proteins can influence oxidative reactions is needed for the development of new antioxidant strategies for oil-in-water emulsions. In particular, environmentally stable systems which can deliver nutritionally beneficial and useful lipids into water-based food, beverage or pharmaceutical products and which are stabilized against oxidation without requiring exogenous antioxidant additives are needed.